This invention relates to an electrolyte replenishing system and more perticularly to an electrolyte replenishing system for a laminated type fuel cell for replenishing electrolyte such as a phosphoric acid into the fuel cell from its exterior.
FIG. 1 is a sectional view showing a prior-art laminated type fuel cell disclosed, for example, in Japanese Patent Application Laid-Open No. 58-165265. In FIG. 1, an electrolyte replenishing throat 1 for replenishing electrolyte into the fuel cell from its exterior is connected to a cooling plate 2. In order to distribute the electrolyte replenished by the electrolyte replenishing throat 1 to each cell in a stack, electrolyte conduits 3 are provided through respective reservoirs 5 which are formed on separator plates 4. Numeral 6 designates a porous nonconductive cell matrix. Electrodes are placed on both sides of the cell matrix 6, not shown in the figure. In the FIG. 1, the laminated type fuel cell comprises a plurality of cell blocks 7 which are stacked on each other, each cell block 7 being composed of five cells containing the cooling plate 2 as one unit.
According to the above constructions, the replenished electrolyte is supplied through the electrolyte replenishing throat 1 passes through the electrolyte conduit 3 and fills the respective reservoirs 5 of the five cells forming the cell block 7. Then, the electrolyte reaches the cell matrix 6 and is stored therein. When the cell matrix 6 is filled with the electrolyte, the fuel cell will be operable.
A problem arises in the prior-art electrolyte replenishing system for a laminated type fuel cell in that the electrolyte must be replenished for each cell block of the fuel cell and also for each time the electrolyte is used up. Further, to save time for supplying the electrolyte to each cell block, an electrolyte tank is connected directly to the electrolyte replenishing throat 1. However, this connection will result in excess head pressure to the lower cell block and in overflowing the electrolyte within the cell portion, which will prevent the fuel cell from operating normally.
Another problem arises in that since the cells in each cell block are electrically conductive with respect to each other through the electrolyte in the electrolyte conduit 3 after replenishing the electrolyte, a part of the output of the fuel cell will be lost as a leakage current and at the same time the separator plate 4 will be corroded.
A further problem arises in that when gases remain within the electrolyte conduit 3 or reservoir 5, the replenishment of the electrolyte will not be performed properly or it will become time-consuming.